An electrostatic paint system consists of a paint booth or enclosure in which a coating such as paint is applied to parts, a conveyor for carrying parts into and out of the booth and an electrostatic paint applying system. The paint applying system includes an atomizing device which receives a fluid column of paint and atomizes it into finely divided paint particles, places an electrical charge on the particles, creates an electrical field between the device and ground, imparts a velocity to the paint particles which directs them toward the grounded part to be coated and meters the paint. Electrically charged paint particles are attracted to and have an affinity for the grounded object to be painted since the grounded object assumes a polarity opposite that of the atomizing device. The charged particle, acted upon by the electrical field, can be deflected from its original trajectory in the direction of the grounded object.
In an automatic electrostatic system, the atomizing device may be mounted in a fixed position, attached to a gun mover device that provides reciprocating motion, attached to a robot that imparts a predetermined complex motion or manipulated manually. An electrostatic atomizer greatly increases paint transfer efficiency from the gun to the surface to be coated as compared to a non-electrostatic device. Electrostatic systems apply paint at transfer efficiencies in the 50%-80% range. Transfer efficiency rarely approaches 100%.
The atomized paint that is not applied to the part is generally referred to as overspray. Overspray consists of paint that misses the part due to rebound from the part surface and paint particles electrostatically deflected to other grounded surfaces such as the spray booth metal components and article conveyors. Most overspray is entrained in the spray booth exhaust air. A significant amount is deposited on the spray booth ceiling, conveyor protection and conveyor. Paint accumulating on these surfaces causes rejects when it drops off on freshly painted parts. This results in downtime for cleaning purposes. This invention relates to a means of greatly reducing paint accumulation on these surfaces.